When yeast spent media from vat fermentation is supplemented and reused, it can outperform fresh culture media, according to researchers at University College Dublin (UCD). This suggests a commercial-scale, circular green economy is feasible for biopharmaceutical fermentation operations. In a recent , UCD PhD student Laura Murphy, postdoctoral researcher Ciara Lynch, PhD, and associate professor David O’Connell, PhD, compared spent yeast culture media to the original rich biological media used to produce recombinant proteins in fermentation.
When growing in either medium, the team identified substantial depletions in levels of six elements and 18 of 20 amino acids. They noted that 98% of the starting levels of magnesium were consumed and found that two to five mM of magnesium were considered ideal for growth. Concentrations of sodium and magnesium were lower in the spent media, while levels of phosphorus, sulfur, potassium, and calcium were comparable to those of rich biological media, the scientists report.
Therefore, they added magnesium and sodium to replenish those levels. In that solution, doubling time for was 1.23 hours, compared to 2 hours for the depleted medium alone.
Simply adding magnesium to the spent solution resulted in a 1.15 hour doubling time, while only adding sodium resulted in a 2.15 hour doubling time.
These results suggest “that magnesium supplementation is the most important elemental addition for successful growth in spent yeast media,” O’Conn.
